Overload release mechanism



Sept. 23, 1941. F. R. NELSON OVERLOAD RELEASE MECHANISM 2 Sheets- Sheet1 Filed Sept. 6, 1940 Sept. 23, 1941.

F. R. NELSON OVERLOAD RELEASE MECHANISM Filed Sept. 6, ,1940 2Sheets-Sheet 2 Patented Sept. 23, 1941 OVERLOAD RELEASEMECHANISM FloydR. Nelson, Rockford, 111., assignor to Gotta Transmission Corporation,Rockford, 111., a corporation of Illinois Application September 6, 1940.Serial No. 355,701

This invention relates to a new and improved 20 Claims.

overload'release mechanism for electric motordriven devices, as, forexample, motor-driven domestic stokers. I i

In the past, stokers have ordinarily been equipped with shear pin typerelease mechanisms, but these have been objectionable because oftheadded work connected with replacing the shear pin when the stoker hasbeen automatically shut off by reason of jamming of the feed screw. Itis therefore the principal object of my invention to provide a releasemechanism of a simpler and more economical construction wherein thedrive is disconnected in the event of excessive resistance to turning ofthe driven shaft of the feed screw driving transmission and the motorcircuit is also automatically broken to stop the motor, the mechanismbeing devoid of any shear pin but having instead a kick-out member whichrequires only resetting after it is kicked out due to the overload, theresetting being as simple as pressing a button.

Another important object of v the invention consists in incorporatingthe kick-out member in' the belt driven pulley where the manuallyoperable resetting pin or knob thereon is easily accessible.

,Still another object consists in providing the motor switch j in ahousing arranged to be mounted in proximity to the pulley where a rotarypendant switch-operating member carried by thehousing is arranged to bestruck by the reset pin only when the kick-out member has been kickedout, whereby to open the switch.

The pendant member when swung upwardly is i arranged to be lockedreleasably in the open circuit position by a latchmember one side ofwhichbears against the spring-pressed plunger of the switch and theother side of which has a detent notch therein to accommodate thependant member in the raisedopen circuit posi- Fig. 2 is a sectionsimilar to a portion of Fig.1; showing the motor switch-operatingmechanism in Vertical section in the plane of the line 22 ofFig.6; "1

Fig. 3 is aview of the inner side ofthe pulley taken on the line '3--3of 'Fig. 1 with a portion of the cover plate broken away for betteril-'- lustration; v Fig. 4 is a similar view showing the kick-out memberin the kicked out position; FigQB is a rear view of the switch housingindicating diagrammatically the radius of operation of the reset pinwith relation to' the'switchoperating mechanism under normal conditions,and Fig. 6 is a similar view indicating the larger radius of operationof the reset pin after the overload has occurred, and showing the partsof the switch operating mechanismin moved posi tion.

The same reference numerals are applied to corresponding partsthroughout the views.

Referring first mainly to Fig. Lthe reference numeral 1 designates thehousing of a domestic stokerdrive transmission for driving the usualcoal feed ,screw. 8 is the driven shaft of the transmission to which iskeyed as at 9, a hub H). A drive pulley H is rotatable on the bearingportion. l2 of the hub l0 and is retained in place by a washer l3 andcotterpin I4.' The pul ley is of a stepped cone type and is adapted toreceive the V.belt 15 in either one of itsthree grooves according tothespeed .at which the stoker. feed screw is to be driven. Anelectricmotor, not shown, carries the companion stepped cone pulley over: whichthebelt l5 passes, and

' it is' that motor which the switch 16. hereinafter tion. Thelatchmember is arranged to be tripped manually to release the pendant memberafter the kick-out member has been reset and everything is in readinessfor restarting the motor. 'The invention is illustrated in theaccompanying drawings, in which I .Fig. 1 is a longitudinal verticalsection through the drive pulley portion of a stoker drive transmissionshowingthe overload release mechanism ofmy invention, theswitch-operating mechanism .beingshown in this view in vertical sectionon the line l-I of Fig. 5 and the pulley being in section on the brokenline l-l of Fig. 3;

referred to controls. At .l'l there is indicated generally an overloadrelease mechanism incorporated in thepulley, in accordance with myinvention, providing a driving connection .between the pulley H and hubI0 so long as'there is no abnormal increase in resistance to. turning ofthe feed screw as reflected by a proportionate increase in resistance toturning of, the driven shaft 8. I8 is the reset pin or knob projectingfrom the back of the pulley and normally operating on the small radiusa, as indicatedin Fig. 5, but arranged to operate on the. larger radius12', as indicated in Fig. 6, after thbver loadhas caused the releasemechanism .11 to disconnect the pulley II from driving relation to thehub It]. At I9 thereisindicated generally the switch operating mechanismarranged to be operated by the reset pin l8 after the pulley connectionof the pulley- II from driving relation to the hub l0. Most stokers havean obstruction clean-out plate on the end of the coal feed conduit nextto the hopper where the foreign body is usually found to lodge, and oncethe obstruction has been removed and the stoker is ready to resumeoperation it is not necessary with the present invention to replace ashear pin, as in the other stokers having other types of overloadrelease mechanisms. It is only necessary with the present invention toresetthe overload release mechanism I! by depressing the reset pinlgpwhi ch as will soon appear, requires no 1 more efiort than pressing apush button. Then the stokeris in readiness for restarting the motor,and the switch-operating mechanism 9 includes a latch 20, which, as willsoon appear, maybe tripped manually to closethe switch it and3start themotor. N f V V 7 Referring now to Figs. 1, 3 and 4, the overload 3release mechanism I 1' comprises a kickout member 2| pivoted on the webportion 22 of the pulley I, as indicated at 23; This member is elongatedand carries the reset pin or knob 3' on the free; ,endportion thereof intransverse relation thereto projecting freely through a, slot 24 1 in a:cover plate 25 fastened to the rim portion 26' of; the pulley-1| as bymeans of screws 21,

this plate having a central hole 28 provided therein through-whicha-portion of the hub I projects, as clearly appears in Fig.1. A camprojection 29 on the kick-out member 2| intermediate the ends thereofhas its inclined cam surrow-c, the hub I0 is driven with the pulleyandthe-coal feed screwvof thestoker which relies Ior-its drive upon theshaft 8 will accordingly be driven= The leaf-spring 33'mounted on theinlengagement with theinner head end of an f adjustable screw 35 mountedradially'in the rim 26.61? the pulley has a bent free end portion .36--arranged to hold the kick-out member 2| in drivinglposition againstthe c-amaction of the projection 29 onthe drive pin 32 tending to kickmember, due to the fact that there is no shoulder on the leaf-springobstructing the return movement and only slight deflection of the spring33 is required, as should be clear from a study of Fig. 4. The pin orknob l8 projects sufliciently from the pulley II, as clearly appears inFig. 1, so that it is easy to press inwardly on it in the direction ofthe shaft Bto reset the kickout member 2| from the position of Fig. 4 tothe position of Fig. 3. By adjustment of the screw 35 inwardly towardthe spring 33, the 7 force required to kick out the member 2| against 1face or' s'houIder 30 arranged slidably to engage the camsurfaceorshoulder 3| on a drive pin 1 32 mounted in the hub, I U andprojecting radially'therefrom; =So long-as the-cam projection j .29 :isdisposed in engagement with the drive-pin 32, as shown imFig.3,:whereinthe directionof j rotation ofthe pulley isindicated by thearweb 22- ofthe pulley on a stud 34and disposed out thdmember 2| towardthe position shown 1 inf-Figiil wherein .the freefendportion .of thekick-outlmember -2|-.is disposed in engagement .with' the .extreme outerend portion 31. of the j leafi-fsprin'g33 in engagement with astopBBpro- 'yidedgby the, end portion of the spring which isbent'lapproximately at right angles toward the kickeoudmember. The bentportion. 36 of the l leafrspring-33 is so inelined in relation to theiirounde'digfree, end .39 of. the kick-out, member andextendstransversely. relative to the path of movement." of the end portion ofthe kick-out member so that "a certain predetermined force is frequired. to niove the kick-out member 2| outwardly against theresistance of the sprin .33, i this tom's being, on 'theotherhand, manytimes greater than that required to return the kick-out janism 9.

resistance of the bent end portion 36 of the spring 33 can be greatlyincreased, while, on the other hand, outward adjustment of the screwaway from the spring 33 will decrease the force necessary to kick outthe member 2|. In that way, it is a simple matter to set the releasemechanism IT to disengage the pulley II from driving relation to the hubl0 within a certain range above thenormal resistance to turning of theshaftB, so that on the one hand there will be no danger of the coal feedscrew drive being disengaged due toa slight fluctuation in the amount ofpowerrequired to turn the feed screw, and on the other hand there willbe no question in regard to the positive disconnection of the drive whena spike, rock, or other serious obstruction, causes jamming of the feedscrew. The screw 35 will, of course, be properly adjusted at thestokermanufacturers plant and should not require readjustmentthereafter. A lock nut 40 on the screw is arranged to be tightenedagainst the rim 25 of the pulley to secure the screw in its adjustedposition.

Referring now principally to Figs. 2, 5 and 6, attention is again calledto the fact that the pin 13 under normal driving conditions moves in acircle having the small radius indicated at a in Fig. 5, whereas upondisconnection of the pulley I from driving relation to the shaft 8 byreason of the kicking out of the member 2|, due to unusually greatresistance to the turning of the shaft 8, the pin l8 in the subsequentfree turning of the'pulley 'moves in a circle'having the larger radiush, indicated in Fig. 6. The switch It, previously mentioned, is mountedwithin a housing 4| suitably secured-to the housing 1 of inFigs. 1 and2] Electrical conductors for the motordriving the pulley l are extendedthrough conduit entered in the hole 43 in oneside of the housing 4| inproximity with the switch 6. The switch It may, of course, be of anysuitable or preferred type, but is preferably of a snap action type'tosnap on and ofi having a spring p'ressed plunger 44 tending normally tomove outwardly toward closed circuit position but arranged to be movedinwardly to open circuit position by the latch 2|],previously mentioned,forming 'a part of the switch-operating mechanism M. The latch ispivoted at one end inside the housing 4| on a pin 45 and engages theplunger 44 intermediate its ends, the free end portion'of the latchextending through a slot 46 in the top wall of the housing so as toprovide a handle portion for convenient manual operation of the latch.The latch has a notch 41 therein on that side thereof opposite the placewhere the plunger 44 at the switch It engages the latch. 68 is a rotarypendant member which also forms a part of the switch-operating mech- Thependant member 48 isin the form of a generally O-shaped rod pivotallymounted by its horizontal upper end portion 49 in bearings 50 providedtherefor in the housing 4|, the member 48 normally hanging vertically.

with the lower horizontal end portion-5| thereof disposed in the samevertical plane in which the reset pin I8 moves but slightly above thecircle of movement, as indicated in Fig. 5. However, when the member. 2|is kicked out to the position shown in Fig. 4, causing the reset pin l8to move in the circle of larger radius, as indicated in Fig.

6,,the pin l8 in the rotation of the pulley will strike the lower endportion of the pendant member 48 and cause it to swing upwardly towardengagement in the notch 41 in the latch 20. Usually the speed at whichthe pin l8 strikes the pendant member 48 is enough to cause the latterto swing upwardly with sufficient force on the very first encounter toengage in the notch 41. At any rate, the second or third revolution ofthe pulley after it has been disconnected from the hub II] willcertainly result in the pin l8 striking the pendant member 48 hardenough to move the latter to the full line position shown in Figs. 2 and6. In the upward swinging movement of the pendant member 48, the bentend 52 slides along the straight edge 53 of the latch member 20, movingthe latter from the inclined dotted position, shown at d in Fig. 2, to asubstantially vertical position slightly to the right of the full lineposition of Fig. 2, but when the end 52 of the pendant member 43 ridesinto the notch 41, the latch 20 moves to the left under the action ofthe spring-pressed plunger 44, gripping the pendant member in the raisedhorizontal'position. In the movement of the latch member 20 from thedotted line position (i of Fig. 2 and finally to the full line positionof Fig. 2, the plunger 44 of the switch I6 is moved to the right enoughto snap the switch to off position, breaking the circuit for the motordriving the pulley ll. Promptly thereafter the pulley ll stops andeverything remains at a stand still until the spike or other obstructionwhich caused the feed screw to jam is removed. Then, the reset pin 18 isdepressed to move the kickout member 2| back to driving position,whereupon the latch 20 is moved to the right just enough to release thependant member 48 holding the switch IS in open circuit position. Then,upon release of the latch 20, the plunger 44 moves outwardly underspring action causing the switch Hi to snap to closed circuit positionso as to restart the electric motor driving the pulley II. It isobviously a much simpler matter to manipulate the reset pin l8 and latch20 than to replace a shear pin. Replacement of a shear pin invariablyrequired calling a service man, whereas the average stoker owner can byobservance of simple instructions take care of everything from clearingout the obstruction at the feed screw to restarting themotor.

It is believed the foregoing description conveys a good understanding ofthe objects and advantages of my invention. The appended claims havebeen drawn with a view to covering all legitimate modifications andadaptations.

I claim:

1. A combination overload release mechanism and motor switch operatingmechanism comprising, in combination, a motor driven drive member, adriven shaft having a drive hub thereon relative to which the drivemember is adapted to turn freely, a drive projection on the hub, akick-out member movably mounted on the, drive member having a driveprojection thereon arranged to engage the aforesaid driveprojecprojecting from the drive member for manual resetting purposes, aswitch for controlling a motor circuit, and means for operating theswitch operable upon engagement therewith by the reset pin, said pinbeing inoperative in relation to said means in the normal position ofthe kickout member.

2.. A structure as set forth in claim 1, including spring means forholding the kick-out member in driving position, and screw threadedadjusting means for varying the spring action so that more or lessresistance to turning of the driven shaft will result in movement of thekickout member from driving position.

3. A structure asset forth in claim 1, wherein the last mentioned meanscomprises a swingable pendant member arranged to be struck by the resetpin to swing it upwardly from a normal dependant position to operatetheswitch to open circuit position, and manually releasable latch means.for releasably locking the pendant member .in a' raised" position so asto keep the switch in open circuit position until manual release of thelatch means.

4.. An overload release mechanism for a drive train, comprising incombination a drive member, a driven shaft having a driv hub thereonrelative to which the drive member is adapted to turn freely, a driveprojection on the hub,

a kick-out member movably mounted on the drive member havinga driveprojection thereon arranged to engage the aforesaid drive projection onthe hub to transmit drive from the drive member to'the shaft, said driveprojections being formed to hav a cam action with respect to one anotherso that the kick-out member is moved from normal drive position whenthere is more than a predetermined resistance to turning of the shaft,and a leaf spring slidably engaging a portion of said kick-out member tohold it releasably either in driving position or inoperative position,the kick-out member being movable manually from inoperative to drivingposition. 5. An overload release mechanism for a drive train, comprisingin combination a drive member, a driven shaft having a drive hub thereonrelative'to which the drive member is adapted kick-out member movablymounted on the drive member having a drive projection thereonarranged toengage the aforesaid drive projection on the hub to transmit drive fromthe drive member to the shaft, said drive projections being formed tohave a cam action with respect to on another so that the kick-out memberis moved from'normal drive position when there is more than apredetermined resistance to turning of the shaft, a reset pin on thekick-out member projecting from the drive member for manual resettingpurposes, spring means for holding the kick out member in drivingposition, and screw threaded adjusting means for varying the springaction so that more or less resistanc to turning of thedriven shaft willresult in movement of the kick-out member from driving position.

I 6. "An overload release mechanismfor a drive train, comprising incombination a rotary drive member and a rotary driven member in coaxialrelationship, one of said members having a sub stantially radialcam-shaped drive projection,

an elongated kick-out'member pivotally mounted at one end on the otherof said members having a cam-shaped drive projection intermediate itsends arranged slidably to engage the first projection, whereby driv istransmitted from the driving to the driven member, and a leafl'springdetent cooperating with the free end of the kick-out member to hold thelatter nor mally in drive position, the free end of the kickout memberbeing slidable past the detent portion of the leaf spring againstresistance of the spring when there is more than a predeterminedresistance to turning of the driven member.

7; A structure as set forth in claim 6, wherein the leaf spring detentis of elongated form and rigidly supported at one end, thedetent'portion being adjacent the other free end, and wherein the freeend portion of said leaf spring is formed to provide a stop projectionbeyond the detent portion to limit movement of the free end portion ofthe kick-out member relative to said leaf springin the kick outmovement.

v 8. A structure as set forth in claim 6, wherein the leaf spring detentis of elongated form and 1 rigidly supported at one end, the detentportion I being adjacent the other free end, and wherein thefree endportion of said leaf spring isformed to provide astop projectionbeyondtheidetent portion to limit movement of the free end porthe leafspring to adjust the tension'thereof relative to the kick-out member andaccordingly makeit more or less easy for the kick-out member to bekicked out.

10.'In a motor drive connection for a motor driven device, thecombination of a housing for said-device, adriven shaft extendingtherefrom,

a drive pulley arranged to be driven by a belt from an electric drivemotor, a hub drivingly connected with the shaft and rotatably mountingsaid-pulley, the side of said pulley toward the housing providing arecess annularly with respect to the hub, means providing a shoulder onthe hub, an elongated kick-out member pivoted at one end tothe pulley insaid recess and having a drive lug projecting there from intermediateits 1 ends for engagement with the driving shoulder, th drivingshoulderand lug being formed for sliding camming. engagement relative to oneanother so as to cause the kick-out member to be swung outwardlyrelative to the hub, spring detent means resisting outward movement ofthe kick-out member, a reset pin projecting from the kick out member insubstantially parallel relation to the driven shaft, a motor switchadapted to control the electric circuit for the aforesaid motor drivingthe pulley, a housing for said switch mounted on the first mentionedhousing adjacent the pulley, a pendant member for operating the switchpivotally mounted on the the detent portion to limit movement of thefree 7 'end portion of the kick-out member relative to said leaf springin the kick out movement, and screw threaded adjusting means cooperatingwith housing and hanging with the lower end thereof normally out of thepath of movement of the reset pin but within the path of movementthereof when the kick-out member is kicked out, and

, manually releasable latch means for releasably locking the pendantmember in a raised position withthe switch held thereby in open circuitposition. V j

'11. A structure as set'forth in claim 10,'including screw threadedadjustable means for adjusting the tension of the spring detent meansrelative to the kick-out 'member, substantially asand for the purposedescribed.

12. A structure as set forth in claim 10, wherein the spring detentmember comprises an elongated leaf spring rigidly supported at one endand having a detent portion on the other free end portion thereofarranged to be slidably engaged by the free end portion of the kick-outmember, said spring being formed at the free end thereof to provideastop projection for engagement by the kick-out member in the'kicked outposition, said leaf spring serving'yieldingly mounted'at one "end on thesame member 'with' the kick-out element and having sliding engagementwith a portion of said element at its other end to hold theelementreleasably eitherin driving position or inoperative position,said kick-out element being movable manually from'inoperative to drivingposition, and screw-threaded ad justing means on the same member withthe kick-out element and leaf spring having engagement with the leafspring at a point intermediate the ends thereof to increase or decreasethe pressure of said leaf spring on the kick-out element.

14. A drive control mechanism comprising, in

combination with relatively rotatable driving and driven members, akick-out element oscillatably mounted on one of 'said'members formovement to and from driving position, the kick-out element having adriving projection arranged to have sliding engagement with a surfaceprovided on the other of said members, an elongated leaf spring mountedat one end on the same member with the kick-out element and havingsliding engagement with a portion of said element at its other end tohold the element releasably either in driving position or inoperativeposition, said kick-out element being movable manually from inoperativeto driving position, and screwthreaded adjusting means on thesamermember with the kick-out element and leaf spring having engagementwith the leaf spring at a point intermediate the ends thereofto increaseor decrease the pressure of said leaf spring on the kick-out element.

15. An automatic control mechanism comprising, in combination, anoscillatable kick-out member, an elongated leaf spring rigidly supported at one end and having a stepped free end portion for slidingengagement with the free end of the kick-out member to hold itreleasably on one step in operative position or on another step ininoperative position, the kick-out member being movable manually frominoperative to operative position, and screw-threaded adjusting meanshaving engagement with the leaf spring at a point intermediate the endsthereof to increase or decrease the pressure of the stepped end portionof said leaf spring on the kick-out member.

16. In a motor drive connection for a motor driven device, thecombination of a housing for said device, a driven shaft extendingtherefrom, a drive pulley arranged to be driven by a belt from anelectric drive motor, a hub drivingly connected with the shaft androtatably mounting said pulley, the side of said pulley toward thehousing providing a recess annularly with respect to the hub, meansproviding a driving shoulder on the hub, an elongated kick-out memberpivoted at one end to the pulley in said recess and having a drive lugprojecting therefrom intermediate its ends for engagement with thedriving shoulder, the driving shoulder and lug being formed for slidingcamming engagement relative to one another so as to cause the kick-outmember to be swung outwardly relative to the hub, spring detent meansresisting outward movement of the kick-out member, a reset pinprojecting from the kick-out member in substantially parallel relationto the driven shaft, and impact operated circuit control means forcontrolling the electric circuit for the aforesaid motor driving thepulley, said means being arranged to be struck by the reset pin when thekick-out member is kicked out.

17. A structure as set forth in claim 16, including screw-threadedadjustable means for adjusting the tension of the spring detent meansrelative to the kick-out member, substantially as and for the purposedescribed.

18. A structure as set forth in claim 16, wherein the spring detentmember comprises an elongated leaf spring rigidly supported at one endand having a detent portion on the other free end portion thereofarranged to be slidably engaged by the free end portion of the kick-outmember, said spring being formed at the free end thereof to provide astop projection for engagement by the kick-out member in the kicked outposition, said leaf spring serving yieldingly to hold the kick-outmember in such position.

19. An impact operated circuit control means comprising, in combinationwith impact means rotatable with a rotary member, a swingable pendantmember on an adjacent support arranged to be struck by said impact meansto swing it upwardly from a normal dependent position to a switchoperating position, a switch operable by said pendant member in raisedposition, and manually releasable latch means for releasably locking thependant member in raised position.

20. An impact operated circuit control means comprising, in combinationwith impact means rotatable with a rotary member, a swingable pendantmember on an adjacent support arranged to be struck by said impact meansto swing it upwardly from a normal dependent position to a switchoperating position, a switch having a spring-pressed plunger tendingnormal- 1y to move outwardly toward one extreme position but arranged tobe moved inwardly to another extreme position when the pendant member isswung upwardly, and a latch member for releasably locking the pendantmember in raised position While holding the plunger of said switch inthe last-named extreme position, the spring pressure on said plungercausing said latch member to grip the pendant member resiliently.

FLOYD R. NELSON.

